Gyroscopes are known instruments which can be used for measuring the Coriolis force or for maintaining orientation. The first gyroscopes included a wheel spinning at high velocity. A typical modern version of the gyroscope includes a vibrating mass implemented as a micromechanical system (MEMS), also known as a MEMS gyroscope.
A vibrating mass has a tendency to continue vibrating in the same plane when its support rotates. The Coriolis effect causes the vibrating mass to exert a force on its rotating support. By measuring this Coriolis force, the rate of rotation of the support may be determined.
The vibrating mass of a MEMS is suspended by resilient members, such as springs. In use, the vibrating mass is brought into oscillation by a drive. The drive is powered by an external source. The external source typically provides an alternating signal, such as a sinus waveform, with a frequency around the oscillation frequency of the suspended vibrating mass.
The MEMS gyroscope provides an output signal which can be used to provide an indication of the Coriolis force. MEMS gyroscopes are typically integrated in electronic products, such as consumer products. MEMS gyroscopes, when integrated in a product, may be used to measure orientation and/or rotation of the product.
MEMS gyroscopes may be provided with a quadrature error compensation circuit to compensate for the so-called quadrature error. This error can be caused by the vibrating direction of the mass not being fully in line with the driving direction, resulting in an undesired vibration component perpendicular to, that is in quadrature with, the driving direction.
A disadvantage of current MEMS gyroscopes is that the accuracy with which they measure the Coriolis force varies over time. In particular, the quadrature error typically increases over time, as a typical quadrature error compensation circuit is incapable of effectively compensating for temperature changes and mechanical stress that may occur during the lifetime of the MEMS gyroscope.
The figures are purely diagrammatic and not drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals.